Effect of the Lattice and Spin-Phonon Contributions on the Temperature Behavior of the Ground State Splitting of Gd{sup 3+} in SrMoO{sub 4}
The temperature behavior of the EPR spectra of the Gd{sup 3+} impurity center in single crystals of SrMoO{sub 4} in the temperature range T = 99–375 K is studied. The analysis of the temperature dependences of the spin Hamiltonian b{sub 2}{sup 0}(T) = b{sub 2}(F) + b{sub 2}(L) and P{sub 2}{sup 0}(T) = P{sub 2}(F) + P{sub 2}(L) (for Gd{sup 157}) describing the EPR spectrum and contributing to the Gd{sup 3+} ground state splitting ΔE is carried out. In terms of the Newman model, the values of b{sub 2}(L) and P{sub 2}(L) depending on the thermal expansion of the static lattice are estimated; the b{sub 2}(F) and P{sub 2}(F) spin-phonon contributions determined by the lattice ion oscillations are separated. The analysis of b{sub 2}{sup 0}(T) and P{sub 2}{sup 0}(T) is evidence of the positive contribution of the spin-phonon interaction; the model of the local oscillations of the impurity cluster with close frequencies ω describes well the temperature behavior of b{sub 2}(F) and P{sub 2}(F).